Starter for multiple electrode lamps



Deca 1965 J. R. CLARK ETAL 3,222,570

STARTER FOR MULTIPLE ELECTRODE LAMPS Filed NOV. 23, 1962 INVENTORS. 7John A. Clark M T- 50 By Glee David Jn Lloyd l/\/. Fuller United StatesPatent STARTER FQR MULTIPLE ELECTRQDE LAMPS John R. Clark and GleeDavid, .Iiu, Tulsa, and Lloyd W.

Fuller, Okrnulgee, Okla assignors to Midwestern linstruments, llnc.,Tulsa, @kia, a corporation of Oklahoma Filed Nov. 23, 1962, Ser. No.239,637 Claims. (Cl. 315-124) This invention relates generally tocircuitry for igniting and operating gaseous discharge lamps and, morespecifically, to circuitry for providing the necessary starting andoperating voltages for gaseous discharge lamps provided with a startingelectrode in addition to the normal cathode and anode electrodes.

Gaseous discharge lamps, whether of the mercury vapor or the inert gastype, have certain physical charac teristics which make the operationthereof substantially different from the operation of other types oflamps. One salient characteristic is the necessity for applying a veryhigh voltage to the discharge electrodes of the lamp during startingthereof which, subsequent to starting, must be substantially reduced.

Many gaseous discharge lamps are provided with a starting electrode inaddition to the normal cathode and anode electrodes to facilitate theapplication thereto of a high starting voltage and thus the ignition ofthe lamp.

Recently, Xenon gas lamps have become available with a startingelectrode in addition to the usual electrodes. These lamps areespecially suited for utilization with direct reading oscillographs but,for maximum utility, the problem of starting these lamps has existedheretofore unless relatively heavy and bulky power supplies wereutilized. This factor becomes especially important when theseoscillographs are to be utilized in aircraft where weight and space isat a premium. Furthermore, the rarefied atmosphere creates an additionalproblem in that flashover external of the lamp and the power supplycomponents often occurs due to ionization of the rarefied gases. Thiscan only be held at a minimum and thus the operational altitudeincreased if the high voltage starting circuitry is made as simple aspossible to facilitate the insulation thereof and isolation from the lowvoltage operating circuitry.

It is, therefore, an object of this invention to provide ignitioncircuitry for a gaseous discharge lamp having a starting electrode asabove described, such ignition circuitry being provided with means forrepeatedly applying high voltage pulses to the starting electrode untilproper ignition occurs.

It is another object of this invention to provide ignition circuitry fora gaseou discharge lamp having a starting electrode as above described,such circuitry being provide-d with means for automatically renderingthe ignition circuit inoperative after proper ignition of the lamp hasoccurred.

It is still another object of this invention to provide igniting andoperating circuitry for a gaseous discharge lamp having a startingelectrode wherein isolation of the low voltage operating circuit and thehigh voltage ignition circuit is achieved.

It is still another object of this invention to provide igniting andoperating circuitry for a gaseous discharge lamp enabling operation ofthe lamp in rarefied atmosphere without external discharge duringignition.

It is yet another object of this invention to provide an ignitioncircuit for a gaseous discharge lamp utilizing an electro-mechanicalactuator coupled with switch structure for cyclically operating thelatter to enable a capacitor coupled with the switch structure to berepeatedly charged by a source of electrical energy and discharged3,222,570 Patented Dec. 7, i965 through the starting electrode of thelamp thereby providing voltages pulses for effecting ignition thereof.

Other objects will become apparent as the detailed description proceeds.

In the drawing:

FIGURE 1 is a schematic circuit diagram of an embodiment of the presentinvention especially suited for operation from a Volt AC. power sourceand a relatively high voltage DC. power source; and

FIGURE 2 is a schematic circuit diagram showing an embodiment of thepresent invention especially suited for operation from the power sourceswhich commonly exist on aircraft.

The embodiment of FIG. 1 shows a gaseous discharge lamp generallydesignated 10, having an anode 12, a cathode 14, and a startingelectrode 16. Electrical power for igniting and operating the lamp isobtained from a 115 volt alternating current power source which isimpressed across the primary winding 18 of a transformer 2t). Secondarywinding 22 of transformer 20 is centertapped, the cathode 14 beingconnected to the center tap by conductor 24 which is grounded as at 26.Diodes 28 rectify the output from the secondary winding 22 and capacitor30 filters the rectified output. Conductor 32 from the anode l2completes the power circuit. The turns ratio of transformer 20 may besuch that approximately 50 volts DC. will be placed across the anode 12and cathode 14 when no current is being drawn from the transformersecondary. The exact value of this voltage will be dependent upon theparticular type of lamp Til utilized.

In the power circuit described above it may be noted that a pair ofseries-connected resistors 34 and 36 are interposed in conductor 32.These resistors serve to limit the current in this power circuit afterstarting of the lamp when current is flowing between the cathode andanode thereof. Resistors 34 and 36 will be of a value depending on theoperating current characteristics of the particular lamp utilized, andfor this purpose, resistor 36 may be variable as shown in FIG. 1 toallow adjustment of the load current.

An electro-mechanical relay generally designated 38, having a relay coil40 and a normally closed switch 42, is utilized as an automatic shutolfdevice for the ignition circuitry to be described hereinafter. The coil40 is connected across resistor 34. A resistor 44 may be utilized inseries with coil 40 to limit the current therethrough in accordance withthe operating characteristics of the relay. The contact of switch 42 isconnected to conductor 32. It is to be understood that the designationof switch 42 as normally closed indicates that the switch is closed whencoil 4th is de-energized. Similar nomenclature will be utilizedthroughout this specification.

The ignition circuitry of FIG. 1 comprises a capacitor 46, an ignitiontransformer 43, and an electro-mechanical relay generally designated 50.Relay 50 comprises a relay coil 52, a normally closed switch 54, and asinglepole double-throw switch 56 normally closed with its upper contactas shown in FIG. 1. A diode 58 is connected across relay coil 52 andserves as an arc suppressor for eliminating inductive voltage peakscaused by the back of coil 52 during de-energization thereof. It shouldbe understood that the negative electrical side of the positive DC.potential shown connected to switch 56 is grounded. Therefore, capaictor46, being grounded at 60, is connected across the DC. power source whenswitch 56 is in the normal position as shown.

The operation of the circuitry shown in FIG. 1 will now be explained. Itshould be understood at the outset that the circuitry as shown willautomatically maintain the lamp 1t} operative indefinitely. Therefore, asuitable 3% switch or switches (not shown) would normally be utilized inpractice to connect and disconnect the power sources from the circuitrydepending on whether or not operation of the lamp is desired.

It may be appreciated that the power circuit commencing with the 115volt AC. power source maintains a voltage across anode 12 and cathode 14at all times through connection therewith by conductors 32 and 24. Thisvoltage, however, is insufiicient to ignite the lamp and servesprimarily to operate the lamp once ignition has been completed. Thereis, of course, a certain open circuit voltage that must be maintainedacross anode 12 and cathode 14 in order for emission therebetween tooccur upon application of the ignition voltage to the starting electrode16. As mentioned above, this open circuit voltage is chosen according tothe operating characteristics of the lamp, and the values of resistors34 and 36 are chosen to provide the proper operating voltage and currentafter ignition.

A circuit traced from secondary winding 22, along conductor 32, throughswitch 42, conductor 62, switch 54 and relay coil 52 to ground at 64,indicates that the relay coil 52 will be energized as long as switch 54is in the closed position. A resistor 66 may be interposed in conductor62 to control the energizing current in coil 52. However, once coil 52becomes energized sufiiciently to open switch 54, the coil thenautomatically becomes deenergized and switch 54 is allowed to reclose.Therefore, it may be appreciated that a buzzer action is produced in therelay 50. The high inertia of the relay switches 54 and 56 enable thesame to move to their energized positions momentarily prior to beingreturned to their normal positions under the action of the relaysprings. The speed of this buzzer action may be controlled by properrelay selection. Furthermore, it has been found that the diode 58connected across relay coil 52 assists in momentarily holding coil 52 inthe energized state after the power circuit thereto is interrupted bythe opening of switch 54.

The engagement of switch 56 with its lower contact during momentaryenergization of relay coil 52 permits the electrical energy stored incapacitor 46 to be transmitted along conductor es and through theprimary winding 70 of ignition transformer 48. The ground connection 72completes the circuit from capacitor 46 through primary winding 70.Capacitor 46 is thus alternately charged across the DC. power source andthen discharged through primary winding 70 due to the buzzer action ofrelay 50.

Since very high voltages relative to the normal operating voltage oflamp 10 are frequently required for ignition, the secondary winding 74of ignition transformer 48 may be provided with a very large number ofturns as compared with the primary winding 70. Ignition transformershaving turns ratios enabling the stepping up of a primary windingvoltage on the order of 200 volts to secondary winding voltages on theorder of 30 kilovolts are conventional items. The pulsed high voltageoutput of secondary '74 is thus applied to the starting electrode 16along conductor 76, and an arc is struck from starting electrode 16 tocathode 14 when ignition occurs. The pulses will continue until thisignition occurs, it being apparent that a series of high voltage pulsesas provided 'by the invention assures reliable starting. It should beunderstood that the polarities of the DC. power source may be reversedand an arc struck from the starting electrode 16 to the anode 12 withequal effectiveness.

Upon ignition of the lamp 10 the emission between anode 12 and cathode14 causes current to flow in conductors 24 and 32 of the power circuitemanating from the 115 volt A.C. source. A voltage drop thus occursacross resistor 34 which energizes relay coil 40. This opens switch 42and interrupts the circuit through conductor 62 thus disconnecting relaycoil 52 from its energizing power source. This automatically terminatesthe operation of the ignition circuit.

When the present invention was conceived, one contemplated utilizationthereof was with Xenon lamps in oscillographs in aircraft where the sizeand weight of components must be kept at a minimum. This created aspecial problem, however, because of the particular voltages availablefrom air-borne power supplies. It is common in aircraft, particularlymilitary aircraft, to provide a variety of AC. voltages including theusual 115 volt A.C. supply. However, 28 volts DC). is the common D.C.supply, and DC. voltages greater than 28 volts are seldom available. Itmay be appreciated that this presents a special problem with regard tothe operation of xenon or other gaseous discharge lamps because acomparatively high DC voltage is not readily available for chargingcapacitor 46 and then pulsing the primary winding of ignitiontransformer 48, wherein the pulse is boosted to the very high startingvoltages required.

The basic principles of operation of FIG. 2 are essentially identicalwith that as shown and discussed above for FIG. 1. However, it may benoted that an additional switch 7 8 is ganged with switch 42 of relay 38and fewer power supply components are utilized. The transformer 20 andits associated rectifiers 28 and filter capacitor 30 utilized in FIG. 1are large, heavy components and thus are not readily acceptable forutilization in aircraft if a more lightweight, compact unit of equaleffectiveness can be provided.

FIG. 2 overcomes the aforementioned disadvantages in a manner to be nowfully described. It should be understood from FIG. 2 that the negativeelectrical side of the 28 volt D.C. supply is maintained at groundpotential along with the return for the 115 volt A.C. supply.Furthermore, the components in FIG. 2 identical in physicalcharacteristics and function to the components in FIG. 1, are designatedby reference characters common to the two figures.

The positive 28 volt D.C. supply lead is connected with resistor 34. Acircuit traceable from resistor 34 through switching diode 80, conductor82, anode 12, and cathode 14 to ground at 84 provides the operatingvoltage and current for lamp 1% after ignition thereof. During ignitionhowever, diode is nonconducting and thus the 28 volt D.C. supply isisolated from the remainder of the circuit.

The additional switch 7 8 added to relay 38 is connected with the 115volt A.C. supply lead. Conductor 86 connects the contact of switch 78 toa resistor 38 in series with a diode 90 which is connected to the uppercontact of switch 56, said upper contact being engaged by switch 56 whenthe same is in its normal position. The remainder of the ignitioncircuitry is identical to that shown and described for FIG. 1.

A conductor 92 connects the contact of switch 78 with a resistor 94 inseries with a diode 96 connected to junction point 98. A capacitor isconnected from junc tion point 98 to ground at 84. Conductor 82 from theanode 12 of lamp It} also is connected with junction point 98.

It may be appreciated that in FIG. 2 the rectifying action of diodeprovides a path for the flow of unidirectional current from the voltA.C. supply lead along conductor 92, through resistor 94 and diode 96,to junction point 98, and thus across capacitor 100 to ground at 84.Resistor 94 is of a value such that the voltage developed acrosscapacitor 1% equals the proper open circuit supply voltage across anode12 and cathode 14 for starting thereof when ignition pulses are appliedto starting electrode 16. As discussed above, this voltage is generallyon the order of 50 volts. The diode 90 also serves to rectify thevoltage from the 115 volt A.C. supply and thus enables capacitor 46 tocharge when switch 56 is in its normal position.

Resistor 88 may be chosen to provide the proper time.

constant for the R.C. combination of resistor 88 and capacitor 46.Electrical power for the energization of relay coil 52 is obtained fromthe 28 volt D.C. supply lead by circuit traceable through resistor 34,switch 42, conductor 62, switch 54, and relay coil 52 to ground at 64.Therefore, except for the above described re-arrangement of the powersources, the circuit of FIG. 2 during the ignition phase functions in anidentical manner to the circuit of FIG. 1.

Once ignition of the lamp is achieved, it is requisite that the powersource for the operation of the cathodeanode emission be transferredfrom the 115 volt A.C. source to the lower 28 volt D.C. source. Thistransfer is achieved in part by fixing the ohmic value of resistor 94high relative to the ohmic value of resistor 34. Therefore, thecomparatively heavy current demanded by the cathode-anode circuit oflamp it} after starting occurs tends to load the 28 volt D.C. supply.Diode 8% is thus placed in the conductive state and the voltage dropacross resistor 34 energizes coil 40 of relay 38 to thereby open switch78 and disconnect the 115 volt A.C. lead from the circuitry. Thisactuation of switch 78 along with switch 42 (as above described forFIG. 1) thus terminates the operation of the ignition and thecathode-anode starting voltage circuitry.

It may be readily appreciated by those skilled in the art that fixingthe ohmic value of resistor 94 relatively high as compared with thevalue of resistor 34 is realizable due to the difference in the voltagesof the AC. and the DC. supplies and the difference in the functions ofthe circuits associated with the two resistors. Capacitor 10d, ofcourse, has no effect on the operation of the lamp 16} once ignition isachieved because the capacitor presents an essentially open circuit tothe DC. supply.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. A circuit for igniting and operating a continuous arc lamp providedwith a starting electrode in addition to the normal discharge electrodescomprising:

first unidirectional electric current supply means having an outputvoltage under load at least equal to the voltage required for continuousoperation of said discharge electrodes;

first circuit means for coupling said discharge electrodes with saidfirst supply means;

electrically responsive switching means coupled with said first circuitmeans and responsive to current flow therein resulting from starting ofsaid lamp;

second unidirectional electric current supply means separate from saidfirst supply means;

switch structure;

electrical energy storing means coupled with said switch structure;

means coupling said switch structure and storing means with said secondsupply means;

second circuit means for coupling said starting electrode with saidswitch structure, the latter having a normal, first switch positionpermitting electrical energy from said second supply means to flow intosaid storing means and a second switch position permitting electricalenergy to flow from said storing means to the starting electrode;

electrically responsive actuator means coupled with said switchstructure for cyclically operating the latter to repeatedly place saidswitch structure in said second position momentarily and then return thesame to said normal position; and

means electrically coupling said actuator means with said first supplymeans and said electrically responsive switching means, the latterinterrupting current flow from said first supply means to said actuatormeans when current flows in said first circuit means, whereby thestarting electrode is pulsed with electrical energy until current flowsbetween the discharge electrodes and hence in said first circuit means.

2. The invention of claim 1, said second circuit means includingtransformer means for increasing the voltage level of the electricalenergy from said storing means.

3. The invention of claim 1, said storing means comprising a capacitor.

4. The invention of claim 1, said actuator means comprising anelectro-mechanical relay including a relay coil having an armaturecoupled with said switch structure and a normally closed switch seriesconnected therewith, said switch opening upon energization of said coilto interrupt current flow through said coil, whereby the latter isalternately energized and de-energized to cyclically operate said switchstructure.

5. A circuit for igniting and operating a continuous arc lamp providedwith a starting electrode in addition to the normal discharge electrodescomprising:

first unidirectional electric current supply means having an outputvoltage under load at least equal to the voltage required for continuousoperation of said discharge electrodes;

first circuit means for coupling said discharge electrodes with saidfirst supply means; electrically responsive switching means coupled withsaid first circuit means and responsive to current flow thereinresulting from starting of said lamp;

second unidirectional electric current supply means separate from saidfirst supply means;

switch structure;

a capacitor coupled with said switch structure;

means coupling said switch structure and capacitor with said secondsupply means; second circuit means for coupling said starting electrodewith said switch structure, the latter having a normal, first switchposition permitting electrical energy from said second supply means tocharge said capacitor and a second switch position permitting electricalenergy to discharge from said capacitor and fiow to the startingelectrode, said second circuit means including transformer .means forincreasing the voltage level of the electrical energy from saidcapacitor during discharge thereof; actuator means comprising anelectro-mechanical relay including a relay coil, an armature for saidcoil, and a normally closed switch operably coupled with said armatureand series-connected with said coil, the switch opening uponenergization of said coil to interrupt current flow through said coil,whereby the latter is alternately energized and de-energized tocyclically operate said armature, the armature being mechanicallycoupled with said switch structure to repeatedly place said switchstructure in said second position momentarily and then return the sameto said normal position in sequence corresponding, respectively, to theenergization and de-energization of said coil; and means electricallycoupling said relay coil with said first supply means and saidelectrically responsive switching means, the latter interrupting currentflow from said first supply means to said relay coil when current flowsin said first circuit means, whereby the starting electrode is pulsedwith electrical energy until current flows between the dischargeelectrodes and hence in said first circuit means. 6. A circuit forigniting and operating a gaseous discharge lamp provided with a startingelectrode in addition to the normal discharge electrodes comprising:

first unidirectional electric current supply means having an outputvoltage under load equal to the required operating voltage for saiddischarge electrodes;

first circuit means for coupling said discharge electrodes with saidfirst supply means;

means interposed in said first circuit means for preventing current flowfrom said first supply means to said discharge electrodes until the flowof current between said discharge electrodes corrunences;

1? electrically responsive switching means responsive to current flow insaid first circuit means and coupled therewith; second unidirectionalelectric current supply means having an output Voltage higher than theoutput voltage of said first supply means, said second supply meansbeing separate therefrom;

second circuit means for coupling said discharge electrodes with saidsecond supply means;

switch structure;

a capacitor coupled with said switch structure;

means coupling said switch structure and capacitor with said secondsupply means;

third circuit means for coupling said starting electrode with saidswitch structure, the latter having a normal, first switch positionpermitting electrical energy from said second supply means to chargesaid capacitor and a second switch position permitting electrical energyto discharge from said capacitor and flow to the starting electrode,said third circuit means including transformer means for increasing thevoltage level of the electrical energy from said capacitor duringdischarge thereof;

actuator means comprising an electro-mechanical relay including a relaycoil, an armature for said coil, and a normally closed switch operablycoupled with said armature and series-connected with said coil, theswitch opening upon energization of said coil to interrupt current flowthrough said coil, whereby the latter is alternately energized andde-energized to cyclically operate said armature, the armature beingmechanically coupled with said switch structure to repeatedly place saidswitch structure in said second position momentarily and then return thesame to said normal position in sequence corresponding, respectively, tothe energization and de-energization of said coil; and

means electrically coupling said relay coil with said first supply meansand said electrically responsive switching means, the latter includingfirst switching means for interrupting current flow from said firstsupply means to said relay coil when current flows in said first circuitmeans, and second switching means electrically independent from saidfirst switching means and interposed in said second circuit means forinterrupting current flow in said second circuit means when currentflows in said first circuit means, whereby the starting electrode ispulsed with electrical energy until current flows between the dischargeelectrodes and hence in said first circuit means, and whereby saidsecond supply means is disconnected from said discharge electrodes aftercurrent fiow therebetween commences.

7. The invention of claim 6, said means preventing current flow in saidfirst circuit means comprising a diode disposed to block current flowfrom said second supply means to said first supply means.

8. The invention of claim 6, said electrically responsive switchingmeans comprising a second electromechanical relay.

9. A circuit for i niting and operating a continuous arc lamp providedwith a starting electrode in addition to the normal discharge electrodescomprising:

first unidirectional current supply means for operating said lamp afterstarting or" the latter, and having an output voltage under load atleast equal to the voltage required for continuous operation of saiddischarge electrodes;

first circuit means for coupling said discharge electrodes with saidfirst supply means;

second unidirectional electric current supply means for furnishingelectrical power to said lamp during starting thereof, said secondsupply means being separate from said first supply means and having anoutput voltage higher than the output voltage of the first supply means;

second circuit means for coupling said discharge electrodes with saidsecond supply means;

electrically responsive lamp starting means coupled With said secondsupply means for producing high voltage ignition pulses; electricallyresponsive switching means coupled with said first and said secondcircuit means for interrupting the electrical continuity of the secondcircuit means in response to current fiow in said first circuit meansresulting from starting of said lamp;

electrically operated means coupled With said switching means and saidstarting means for operating the latter to efiect repetitive productionof said pulses, said switching means being operable to interrupt currentflow to said electrically operated means to cease said pulse productionwhen current flows in said first circuit means; and

third circuit means for coupling said starting electrode with the outputof said starting means, whereby the starting electrode is pulsed withelectrical energy until current flows between the discharge electrodesand hence in said first circuit means, thereby causing disconnection ofthe second supply means from the discharge electrodes and termination01" operation of said starting means.

It). The invention of claim 9, wherein is provided means interposed insaid first circuit means for preventing current flow from said firstsupply means to said discharge electrodes until the flow of currentbetween said discharge electrodes commences.

References Cited by the Examiner UNITED STATES PATENTS 1,961,749 6/1934Ewest 315-289 X 3,115,594 12/1963 Mall0ry 315241 X DAVID J. GALVIN,Primary Examiner.

1. A CIRCUIT FOR IGNITING AND OPERATING A CONTINUOUS ARC LAMP PROVIDEDWITH A STARTING ELECTRODE IN ADDITION TO THE MORMAL DISCHARGE ELECTRODESCOMPRISING: FIRST UNIDIRECTIONAL ELECTRIC CURRNT SUPPLY MEANS HAVING ANOUTPUT VOLTAGE UNDER LOAD AT LEAST EQUAL TO THE VOLTAGE REQUIRED FORCONTINUOUS OPERATION OF SAID DISCHARGE ELECTRODES; FIRST CIRCUIT MEANSFOR COUPLING SAID DISCHARGE ELECTRODES WITH SAID FIRST SUPPLY MEANS;ELECTRICALLY RESPONSIVE SWITCHING MEANS COUPLED WITH SAID FIRST CIRCUITMEANS AND RESPONSIVE TO CURRENT FLOW THEREIN RESULTING FROM STARTING OFSAID LAMP; SECOND UNDIRECTIONAL ELECTRIC CURRENT SUPPLY MEANS SEPARATEFROM SAID FIRST SUPPLY MEANS; SWITCH STRUCTURE; ELECTRICAL ENERGYSTORING MEANS COUPLED WITH SAID SWITCH STRUCTURE; MEANS COUPLING SAIDSWITCH STRUCTURE AND STORING MEANS WITH SAID SECOND SUPPLY MEANS; SECONDCIRCUIT MEANS FOR COUPLING SAID STARTING ELECTRODE WITH SAID SWITCHSTRUCTURE, THE LATTER HAVING A NORMAL, FIRST SWITCH POSITION PERMITTINGELECTRICAL ENERGY FROM SAID SECOND SUPPLY MEANS TO FLOW INTO SAIDSTORING MEANS AND A SECOND SWITCH POSITION PERMITTING ELECTRICAL ENERGYTO FLOW FROM SAID STORING MEANS TO THE STARING ELECTRODE; ELECTRICALLYRESPONSIVE ACTUATOR MEANS COUPLED WITH SAID SWITCH STRUCTURE FORCYLICALLY OPERATING THE LATTER TO REPEATEDLY PLACE SAID SWITCH STRUCTUREIN SAID SECOND POSITION MOMENTARILY AND THEN RETURN TO THE SAME TO SAIDNORMAL POSITION; AND MEANS ELECTRICALLY COUPLING SAID ACTUATOR MEANSWITH SAID FIRST SUPPLY MEANS AND SAID ELECTRICALLY RESPONSIVE SWITCHINGMEANS, THE LATTER INTERRUPTING CURRENT FLOW FROM SAID FIRST SUPPLY MEANSTO SAID ACTUATOR MEANS WHEN CURRENT FLOWS IN SAID FIRST CIRCUIT MEANS,WHEREBY THE STARTING ELECTRODE IS PULSED WITH ELECTRICAL ENERGY UNTILCURRENT FLOWS BETWEEN THE DISCHARGE ELECTRODES AND HENCE IN SAID FIRSTCIRCUIT MEANS.